reaming of square tube 2

[GTO67]

Hi All,

I need to ream / hone or grind about a mm from the inside of a 75 x 5 shs. All ideas appreciated

 

[CoryPad]

I don't know what 75 x 5 shs is, but if you want to take material off the inside of a closed object (especially one with straight walls), broaching would be a good suggestion.

 

[GTO67]

Sorry I should have been more specific. 75 x 75 x 5 (mm) square steel tube approximately 1300mm long with one closed end

 

[MikeHalloran]

To gain 1 mm in 75, assuming the material is steel, you could expand the end.

For which purpose, you could make up some sort of square wedge expander.

Or just fill the portion you want to expand with water, and freeze the assembly.



Mike Halloran
Pembroke Pines, FL, USA

 

[GTO67]

Thanks mike, however I need to remove approximately 1mm in total from the I.D to allow a 65 x 65 steel tube to slide inside the whole way.

 

[MintJulep]

Fill it with acid.

 

[CoryPad]

With the new information, I am inclined to agree with MintJulep.

 

[CorBlimeyLimey]

Can you not reduce the 65 x 65 tube?

Or as Mike first suggested, expand the end of the 75 x 75 tube, and then machine the outer surface back to size.

 

[vpl]

Perhaps a robot to polish the inside?

Heating the tube a section at a time?

Taking the 1 mm from the outside of the inner tube?

Patricia Lougheed

******

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[HDS]

Buy telescoping tubing that is made to fit one inside the other.

It would be easier to make the outside of the male tube smaller than the inside of the female tube bigger.

 

[CorBlimeyLimey]

Oh! I just realised you want the whole 1300mm expanded ... and you have one end closed. That definitely complicates things.

So, 1st choice > reduce the 65 x 65 tube.

2nd > Fabricate a new tube using suitably sized plates or channels.

3rd > Cut the 75 x 75 tube in half (length wise), mill the insides to suit, weld the two halves together.

 

[ornerynorsk]

So is this a one-off or production qty? There is no practical way to expand or broach the ID of a closed end square tube. Buy telescoping tube, as another poster suggested. Uni-Strut and others sell it. If you are dealing with large qty, just have a mill make what you need.

 

[mfgenggear]

GT067

chem milling of the inside seems to be the best idea
there is vendors who specialize in this work.
do not try this your self since working with acid take special safety handling procedures & equipment.


next time it is possible to make the exact square tubing
by using sheet metal formed & welded, welds planished & draw formed (draw bar) to the exact size needed then the end cap welded by a tubing mfg.

MfgEngGear

 

[GTO67]

Thanks so far for all the help. The problem is that the tube in question has already been fabricated in place and the unit has been powder coated and fully assembled. The cost of dissassembling and reassembly far out weighs the cost of the basic structure so it needs to be repaired in place. Fabricating a smaller tube(63x63) to slide inside is the easiest way to go, however the customer needs the unit to conform to the exact standards as their existing units. I am extremely interested in the process of chemical milling so if anyone has any experience or advice in regards to the type of acid and time frame etc. it would really help.
Cheers

 

[TheTick]

Rotsa ruck! Structural tube just isn't made for telescoping. There are a few specialty manufacturers out there that do this. If you need to do this on a production basis, find one.

 

[IRstuff]

Chemical milling is probably unlikely to work on a closed-end pipe. You need to have a constant chemical environment to get uniform milling.

Some sort of electrolytic approach might be possible, i.e., a 1.3-m long electrode that can do one side at a time with electrolyte flowing in the small gap between the electrode and the tube. But that seems absurdly difficult to me; the cost of doing something like would be high.

I fail to see why you can mill the OD of the insert. That would be a 10x easier task.

TTFN

FAQ731-376

 

[TheTick]

EDM?

 

[TheTick]

I'll bet EDM could make a nice tube. You probably would need to start with a thicker wall, though.

 

[berkshire]

You might do it with a sinker type EDM pumping the slurry out of the tube, but you are going to need a bunch of electrodes.
B.E.

 

[IRstuff]

Holding a half-millimeter level over a 1300 mm would be nontrivial and expensive.

TTFN

FAQ731-376